The present invention relates to an image forming system for recording images using electrophotographic developing processes, and more particularly, to a method and apparatus for automatically eliminating a paper jam.
Electrophotographic developing processes are widely used in copiers, printers, facsimile machines and other instruments to generate an image corresponding to an electrical signal. An example of an electrophotographic developing printer is a laser beam printer (hereinafter "LBP"). The general structure of an LBP using the electrophotographic developing process is disclosed in detail in U.S. Pat. No. 5,002,266 entitled "Sheet Feed Apparatus for Image Forming System" issued to Kikuchi et al. on 26 Mar. 1991.
While modern devices, such as the aforementioned printer, greatly enhance our ability to transfer and duplicate information, they also bestow the misfortune of an occasional malfunction. Although some problems are more prevalent than others, one problem that seems to frequently occur is the "paper jam." Paper jams are always inconvenient; however, if they happen at the wrong time, they can cause severe problems in office administration. Therefore, it is greatly desired that when a paper jam occurs, the jam be quickly eliminated. While the prior art teaches a variety of ways in which paper jams can be cleared from electrophotographic devices, these methods have disadvantages of being inconvenient and detrimental to the mechanical health of the device.
One primary technique for automatically eliminating a paper jam is disclosed in detail in Korea Patent application No. 93-9002, assigned to the same assignee as the present invention. With this technique, a circuit controller displays the occurrence of the jam on an operational panel and checks whether the unit's cover is open or closed. The open or closed state of the unit's cover is detected by a sensor. In order to automatically eliminate the paper jam, the user selects a paper jam eliminating mode for performing a paper jam correction operation by opening and closing the unit's cover. Then, since the sensor is consequently switched either on/off or off/on, the circuit controller senses the paper jam eliminating mode through a sensor input. The circuit controller then rotates a fixing roller by activating an engine driving motor which further rotates both a pickup roller and the register rollers. Therefore, paper in the paper conveyance path is ejected, and the paper jam is eliminated. Thereafter, the circuit controller sequentially stops operation of each portion of the engine and activates a standby mode. A control circuit that performs these operations is disclosed in Korean Patent application No. 92-11243, assigned to the same assignee as the present invention.
One problem with the foregoing method is that the opening and closing of the unit's cover causes external light to enter into the interior of the printer. This often causes the photosensitive drum and developing unit to be unnecessarily exposed to light so that their voltage potential varies, and picture quality ultimately deteriorates. Also, since the toner within the developing unit is dispersed in the interior of the printer, internal items such as the photosensitive drum, charger, developing unit, laser scanner unit and laser reflecting mirror become polluted, thus causing subsequent malfunction of the unit. Furthermore, since the unit's cover may have to be frequently opened and closed, the life of the printer is shortened due to vibrations and shock to the printer that accompany opening and closing of the cover.
Another attempt at a paper jam removal method is disclosed in U.S. Pat. No. 4,260,236 entitled Electrophotographic Apparatus issued to Tsuda et al. This reference discloses a record paper detector for detecting a paper jam. Once a jam is detected, a paper jam signal is generated to stop rotation of the photosensitive drum and to move a transfer roller away from the photosensitive drum to facilitate manual removal of the jammed paper. This method, aside from being inconvenient, can require an opening of the unit cover which thereby exposes the drum to exterior light and consequently risks deterioration of the photosensitive drum and developing unit as mentioned above.